The goal of the proposed research is to study the interplay of chemical transmitters on the function of the isolated mammalian parietal cell. In the initial phases of this research, a method of the isolation of viable cells from canine fundic mucosa has been developed. Using oxygen consumption and the accumulation of aminopyrine as indices of response, gastrin, acetylcholine, and histamine were shown to act directly on specific receptors on the parietal cell. Potentiating interactions, which may account for the apparent nonspecificity of cimetidine and atropine in vivo, were found to occur between these three stimulants. Histamine, but not cholinergic agents nor gastrin, was found to increase cyclic AMP production, with this effect correlating with histamine stimulation of parietal cell function. Prostaglandin E2 was shown to specifically inhibit histamine stimulation of both aminopyrine accumulation and cyclic AMP production. In the proposed research, the above studies will be completed and extended to other species including man. The ability of parietal cells to metabolize glucose, fatty acids and amino acids and the effects of stimulation upon these metabolic rates will be investigated to determine which substrates the parietal cell is capable of utilizing for the secretion of acid and to compare the actions and interactions of stimulants upon the rates of substrate utilization, oxgyen consumption, aminopyrine accumulation, and morphological transformation. Other potential stimulants and inhibitors including many of the polypeptides and biogenic amines present in gastrointestinal mucosa will be tested for direct effects of parietal cell function. The role of calcium in mediating the response to cholinergic agents and gastrin will be examined. The direct interaction of biologically active, radiolabeled secretagogues and inhibitors with their specific receptors on parietal cells will be investigated. In preliminary studies, histamine and other endocrine cells have been isolated from fundic mucosa. Histamine was found to be contained in a mast-like cell. Using highly enriched fractions of these cells from fundic mucosa, the pathway involved in histamine formation and release will be studied.